I was thinking that maybe a way people can customize graphics to their own liking, without people needing any Reshade at all, is to have a global post process volume that has global bounds, and over-rides all the other PP volumes in the level.
I was working on a UE4 game of my own for a while and had been planning to do that myself.

Of course you'd need to make sure people can't cheat with it, which could be done by just playing around with the settings and if any give an unfair advantage, don't allow the user to do it.

I know that this can easily destroy the style you intended for the game, however it's becoming obvious that PC gamers in general tend to want as many graphic options as possible. That's why things like Reshade/SweetFX are so popular.